Stacking devices and platforms therefor

ABSTRACT

A platform, for use in a sheet stacking device in which the platform descends as a stack being formed on it grows higher, is so constructed that its length can be varied according to the length of sheets to be stacked. The platform is made in two or more sections (10, 11, 12) each hinged (15, 17) to the next, and all sections are supported horizontally to receive long sheets, less than all the sections being horizontal and the remaining sections hanging vertically when shorter sheets are being stacked. Wheels (13, 16, 18) may be provided on the platform so that it may easily be moved out of the stacking device when loaded, all the sections being restored to a horizontal position for such movement.

This invention relates to sheet stacking devices and more particularlyto platforms on which stacks of sheets may be formed. It is common toemploy such a platform in a sheet stacking device, the platform beinglowered as a stack being formed on the platform increases in height sothat the top of the growing stack remains at a substantially constantlevel as successive sheets are fed on to it. The feed of sheets isnormally along a substantially horizontal path above the stack beingformed; each sheet is projected by feed rollers or belts from one sideof the stack to pass over the stack a small distance above its top untilthe leading edge of the sheet strikes a vertical surface of a"backboard" at the opposite side of the stack, the horizontal movementof the sheet stops and the sheet falls on to the stack.

The distance between the feed rollers or belts and the backboard has tobe set according to the length (measured in the direction of travel) ofthe sheets to be stacked, and when the length of the sheets beingstacked is less than the maximum length that the stacking device canhandle, either the backboard or the feed rollers or belts overlaps partof the platform (as the latter must be at least as long as the maximumsheet length). Such overlap is inconvenient. Also the operator needs towatch the stacking operation and the most convenient position for thisis behind the backboard where often some machine controls are placed. Toreach this position with different sheet lengths the operator usuallyhas to stand on the platform, sometimes on a wooden box, and where theplatform includes a wheeled trolley this could be dangerous.Alternatively sections of the platform may be removable, which is a timeconsuming operation.

It is an object of the present invention to provide an improved stackingdevice, specifically a platform so arranged that these inconveniencesare avoided.

According to the invention there is provided a platform for a sheetstacking device constructed so that its length can be varied in whichsaid platform comprises at least two sections, each of said sectionshaving a pivotal connection to the next section. Preferably said pivotalconnection is a hinge connection, the pivotal axis of each hingeconnection extending at right-angles to the length of the platform. Whensheets of the maximum length are to be stacked, both or all sections ofthe platform are supported in horizontal alignment but if sheets of ashorter length are to be stacked, one or more of the sections may notneed to be so supported and this section or sections hangs down on itshinge connection to the supported section or sections.

The invention may also be embodied in a sheet stacking device having aplatform as set out above, together with lowering means with which oneor more of the platform sections may be engaged, said lowering meansbeing adapted to raise the platform to bring its thus engaged section orsections to a level at which sheets may be received from a sheet feederand to lower the platform as a stack of sheets accumulates thereon, thesection or sections not thus engaged hanging from the engaged section orsections while the latter is/are raised in which said lowering meansincludes two support beams, disposed parallel to the direction of motionof sheets arriving in the stacking device, and spaced apart by slightlymore than the width of the platform.

Each beam may have a plurality of support stubs projecting horizontallytowards the other beam, the number and spacing of the stubs beingrelated to the number and lengths of the platform section; the platformmay be so positioned relative to the stubs that all the platformsections may be supported, or the platform may be displaced lengthwiserelative to the stubs and beams so that one or more sections are notsupported. In the latter case, when the beams are lifted to raise theplatform the unsupported platform sections hang down from one end of thesupported section or sections; when the beams are fully lowered, theplatform is required to be at floor level and the hanging section orsections must be restored to the horizontal position. Conveniently thiscan be done by a rope or chain having one end secured to the free end ofa bar pivotally connected at its other end to one of the beams, and theother end secured to an anchorage so placed as to be above said free endwhen the hanging sections are restored to the horizontal. The platformmay conveniently be provided with at least one pair of wheels on each ofits sections so that, after a stack of sheets has been formed upon it,it may be moved away and a similar platform may be brought into positionbetween the beams to be raised and to have a further stack of sheetsformed upon it.

In order that the invention may be well understood, a preferredembodiment thereof will now be described, with reference to theaccompanying diagrammatic drawings, in which:

FIG. 1 is a side elevation of a platform embodying the invention;

FIG. 2 is a side elevation of a stacking device including the platformof FIG. 1;

FIG. 3 is a plan view of part of the device of FIG. 2.

FIG. 4 is a side elevation of part of a modified form of the platformshown in FIG. 1;

FIG. 5 is a plan view of part of FIG. 4, and

FIG. 6 is a diagrammatic plan view showing the different positionsoccupied by the platform of FIG. 4 when included in the stacking deviceof FIG. 2.

First referring to FIG. 1, a platform 1 is shown which comprises threesections 10, 11, 12, the right-hand section 10 is a long section and thesections 11, and 12 are equal in length to one another and each lessthan half the length of the section 10. The long platform section 10 isprovided with two pairs of wheels 13 mounted under its end portions onaxles 14, 15. The short platform section 11 is provided with a pair ofwheels 16 under its end portion remote from the section 10 and similarlythe short platform section 12 has a pair of wheels 18 under its endportion remote from the section 11, the wheels 16, 18 being respectivelymounted on axles 17, 19.

Hinge connections are provided between adjacent sections of theplatform, i.e. between section 10 and section 11 and section 12. Theaxles 15, 17 serve as pivot pins of the hinge connections. Each of theshort platform sections 11, 12 has a respective extension 111, 121 tothe right (as seen in FIG. 1) under the adjacent end portions of thesections 10, 11 respectively, these extensions being journalled on theaxles 15, 17 respectively.

As shown in full line in FIG. 1, only the platform sections 10, 11 aresupported (by means to be described later) in a horizontal position; theshort section 12 therefore hangs vertically from its hinge connection,through axle 17, to the section 11. The length of the platform is thusequal to the combined length of sections 10, 11. If the section 12 werealso supported horizontally, it would be in the position shown in brokenline and the length of the platform would be equal to the combinedlength of all three sections. It is possible also to support only thelong section 10 in the horizontal position, allowing both the shortsections 11, 12 to hang vertically from the hinge connection throughaxle 15.

In FIGS. 2 and 3 is shown a sheet stacking device including the platform1 described above. Sheets are fed to the device between pairs of rollers2 in the direction shown by the arrow A. Each sheet leaving the rollers2 is travelling at sufficient speed to continue in a substantiallyhorizontal path to the right until it strikes a vertical face of abackboard 3; this stops the sheet which then falls.

Below the path of the successive sheets from the rollers 2 to thebackboard 3, a stack 4 forms as each successive sheet falls on to thepreceding sheet. The growing stack 4 is carried by the platform 1, whichis lowered progressively at the same rate as that at which the height ofthe stack increases; this maintains a constant vertical spacing betweenthe top of the stack 4 and the path of sheets from the belts 2 to thebackboard 3, as is required.

The sheets forming the stack 4 are longer than the platform section 10,but shorter than the combined length of the sections 10, and 11. Asshown in FIG. 2, therefore, only the sections 10, 11 are supported inthe horizontal position; the section 12 is hanging from its hingeconnection to section 11. When the stack 4 is complete, feeding ofsheets is stopped and the platform 1 is lowered to the base 5 of thestacking device, where a pair of rails 50 are provided to receive thewheels 13, 16, 18. Upon reaching the rails 50, it is necessary for allsections of the platform 1 to be horizontal. To achieve this, positionedon each side of the platform when the latter is receiving sheetsthereon, is a chain or cable 51 connected between an anchorage 52 andone end of a bar 71 pivotally attached, at its other end, to mechanismfor raising and lowering the platform, to be described later. The twoanchorages 52 are at a higher level than the rails 50 and the length ofthe chains or cables 51 is such, having regard to the position of theanchorages 52, that as the platform 1 is lowered, the chains or cablesbecome taut before the platform has fully lowered and the bars 71 areswung about their respective pivotal attachments so that they bothengage the section 12 and pull the latter into the horizontal positionas lowering of the platform 1 is completed.

The platform 1 is raised and lowered by four chains 60 which are linkedin pairs by two beams 61, only two of the chains being visible in FIGS.2 and 3. The beams 61 are disposed parallel to the rails 50 and arespaced apart by a distance slightly greater than the width (normal tothe plane of FIG. 2) of the platform 1. The beams are longer than theoverall length of the platform 1 (with all its sections horizontal) andproject beyond the platform at each end, the chains 60 being disposedvertically and attached to the projecting ends of the beams so that allparts of the chains and beams are clear of the stack 4 during itsformation on the platform.

The other ends of the bars 71 are respectively pivotally attached, at 72(see FIG. 3), to a different one of the beams 61, the pivot 72 beingaligned with one of the axles 15, 17 depending on the position of theplatform 1.

Each beam 61 has five platform engaging lifting stubs 62, 63, 64, 65 and66 projecting horizontally from the beam so as to be engageable withblocks fixed to the underside of the platform (see also FIG. 3). Thesection 10 has two blocks 67, 68 fixed on each side thereof, the section11 has one block 69 fixed on each side thereof and the section 12 hasone block 70 fixed on each side thereof. Each of the stubs 62 to 66 isprovided on its upper face with a conical projection and to prevent anymovement of the platform whilst the latter is being raised or loweredthe conical projections engage into respective mating recesses in thebottom faces of the blocks 67 to 70. When the platform 1 has its wheelson the rails 50 and all its length is between the beams 61, three stubs62, 63, 64 from each beam project under the long platform section 10,one stub 65 from each beam under the short platform section 11, and theremaining stub 66 from each beam under the section 12. With the platformso positioned, lifting of the beams 61 by chains 60 causes stubs 62, 64,65, 66 to engage blocks 67, 68, 69, 70 respectively and thus raises theplatform 1 with all its sections horizontal, so that the whole platformis available to receive long sheets.

If medium-length sheets are to be stacked, i.e. sheets no longer thanthe combined length of platform sections 10 and 11, then the platform 1,when it is moved along the rails 50 from the left, is stopped when theblocks 67, 68 of the platform section 10 are respectively above thestubs 63, 65 of the two beams; the blocks 69 of section 11 are thenabove the stubs 66, no stubs are below the section 12, no part of theplatform is above the stubs 62, and no blocks are above the stubs 64.With the platform so placed, when the beams 61 are lifted to raise theplatform, the sections 10, 11 will be held horizontal to receive sheets,section 12 hanging (as in FIGS. 1 and 2). For stacking short sheets, forwhich the platform section 10 is long enough it will be understood thatthe platform is stopped when the blocks 67, 68 of section 10 arerespectively above stubs 64, 66 so that when the platform is raised boththe sections 11, 12 hang vertically as there are no stubs under them.

It will be appreciated that the use of the platform 1 as described aboveenables the backboard 3 to be moved to the left without difficulty whenmedium-length or short sheets are to be stacked, as the horizontallength of the platform 1 during stack formation will be less than itsmaximum length. This is particularly helpful when, as is common, anoperator's position 7 is associated with, and movable with, thebackboard 3.

If the stacking device is arranged so that the rollers 2 are movable toadjust the spacing between the rollers 2 and backboard 3, then theplatform 1 may be used with the long section 10 at the left, the shortsections 11, 12 at the right; the chain or cable 51 and its anchorage 52will then also be at the right of the stacking device and thedisposition of the stubs 62, 63, 64, 65, 66 on the beams 61 will bereversed.

To facilitate the movement of the platform 1 along the rails 50, when acompleted stack of sheets is being removed and when the platform ismoved into the stacking device, the platform is arranged to beself-propelled. The long platform section 10 carries on its underside amotor 73, arranged to drive the axle 15 and hence the wheels 13 on axle15. Transmission of drive from motor 73 to axle 15 is effected by agearbox 74 and a chain drive 75. In view of this the axle 15 necessarilyextends across the width of the platform and has one of the wheels 13secured to it adjacent to each of its ends. The axles 14, 16, 19 howeverneed not extend across the width of the platform, and preferably arestub axles each carrying one wheel.

It is usual to form the stack of sheets on a pallet so that thecompleted stack may conveniently be handled by, for example, a fork lifttruck. Referring now to FIGS. 4 and 5, a modified form of platform 1 isshown with a pallet P of known form on its upper surface. As shown, allthe sections 10, 11 and 12 will remain horizontal when the platform 1 islifted by the beams 61. To enable the operator to place the pallet inthe required position on the platform ready to receive sheets thereon asdescribed above, he releasably fixes a gauge bar 150 across theplatform.

For this purpose the platform 1 is provided with an additional section12a comprising a U-shaped girder 151 lying on one side and carried onextensions 152 which extend under the adjacent end portion of section12, the extensions being journalled on the axles 19 so as to form ahinge connection between the sections 12 and 12a. The section 12a alsohas a pair of wheels 153 positioned so that the upper face of the girder151 is in alignment with the top of the sections 10, 11 and 12 when theplatform is positioned on the rails 50.

The gauge bar 150 comprises a beam 154 provided near each end thereofwith a vertical bolt 155 threaded at its lower end. Slidably mounted onthe beam 154 are a number of settable markers 156 which may be clampedat desired positions along the beam by means of screws 157. Two threadedholes 158 are provided in the upper face of girder 151 (FIG. 6), andsimilar holes 159, 160 are provided respectively in the upper faces ofplatform sections 11 and 12.

The operator places the bar 150 on the section 12a and screws the bolts155 into the holes 158, the right hand face of the beam 154 then forminga stop against which a pallet is placed. This positions the palletcorrectly in the lengthwise direction to receive large sheets whichrequire all sections 10, 11 and 12 to remain horizontal when theplatform is lifted as described above. It often happens that a number ofstacks are formed simultaneously side by side across the width of theplatform 1. In such a case a separate pallet is placed on the platformto support each stack, and to ensure that the pallets are placed in thecorrect positions across the platform the markers 156 are first clampedin the required positions along the beam 154 to indicate the palletpositions. This is illustrated in FIG. 5 which shows two pallets P andP1. As the platform of FIG. 4 is lifted by the beams 61 the section 12ahinges downwardly about axles 19 so that it does not impede the flow ofsheets as they are fed on to the platform.

If the sheet length is such that section 12 is not required to supportthe stack, the gauge bar 150 is placed on the section 12 and the bolts155 screwed into holes 160; and if it is such that only section 10 isrequired to support the stack, the gauge bar is placed on to section 11and bolts 155 screwed into holes 159.

As the lowering of a platform, as shown in FIGS. 4 and 5, is completedthe section 12a will be moved to the horizontal position by the bars 71in the same way as the sections 11 and 12.

Referring now to FIG. 6 three positions A, B, and C indicating differentpositions occupied by a platform 1 during one cycle of operation of thestacking device are shown. Position A is the area where the platform 1is prepared for receiving sheets by having one or more pallets placed onit, position B is the position in the stacking device from which theplatform is lifted and to which it is returned by the beams 61 asdescribed above, and position C is where completed stacks are removedfrom the platform.

The motor 73 is most conveniently an electric motor and the platform maybe provided with any conventional current pick-up devices for bringingan electric current supply to the motor. The energisation of the motor73, and hence the movement of the platform along rails 50, may becontrolled by the operator of the stacking device; in large measurehowever, such control may be automatic from a control device 161 whichmay, for example, be a micro-processor.

In operation, and assuming that a loaded first platform 1 is in positionC and a second platform is being loaded with sheets as described above,the platform at C is unloaded and moved along rails 50, under the secondplatform to position A at which it is stopped when its presence isdetected by a sensor 162. Whilst the first platform is at position A theoperator fixes a gauge bar 150 into position, as described above, Toindicate which platform section (i.e. 11, 12, or 12a) the bar 150 is tobe fitted to, one of three lamps 163, 164, 165 is switched on by thecontrol device 161 according to data fed into the latter (e.g. sheetlength).

After loading of the second platform has been completed, it is loweredto position B and then moved to position C to be unloaded. The firstplatform at position A is then moved to position B in the stackingdevice. The arrival of the platform at the desired position relative tothe beams 61 is detected by one of three sensors 166, 167 and 168. Thelatter each correspond to one of the three positions at which theplatform may be required to stop, according to whether the whole lengthof the platform (i.e. all three sections 10, 11, 12) or only part of itslength (i.e. sections 10 and 11 or section 10 alone) is to be supportedhorizontally during stack formation. The control device responds towhichever one of the sensors 166, 167, 168 corresponds to the length ofsheets to be stacked. Upon completion of the stack and lowering of theplatform the same sensor, or a further sensor, may detect when theplatform is again supported by the rails 50 and may control energisationof motor 73 to propel the platform to position C at which it is stoppedwhen its presence is detected by a sensor 169. Although not shown, itwill be understood that all the various sensors are connected to thecontrol unit 161.

There can be any number of sections making up the platform and in afurther modified form the platform would be constructed in the manner ofa roller shutter.

We claim:
 1. A sheet stacking device including a sheet feeder, aplatform constructed so that its effective length can be varied, saidplatform comprising at least two sections pivoted together, the axis ofeach pivot extending horizontally at right angles to the length of theplatform, means for supporting said platform in a horizontal plane, andlifting means adapted to engage with one or more of the platformsections forming said effective length of the platform, to raise theplatform to bring its thus engaged section or sections to a level atwhich sheets may be received from said sheet feeder and to then lowerthe platform as a stack accumulates thereon, the section or sections notthus engaged hanging down from the engaged section or sections.
 2. Asheet stacking device as claimed in claim 1 in which said lifting meansincludes two support beams extending parallel to the direction of motionof sheets arriving in the stacking device and arranged so as to engageopposite sides of the thus engaged section or sections whilst saidplatform is raised and lowered.
 3. A sheet stacking device as claimed inclaim 2 in which each of said beams has a plurality of support stubsprojecting horizontally towards the other beam, the number and spacingof the stubs being related to the number and lengths of the platformsections.
 4. A sheet stacking device as claimed in claim 1 includingmeans to drive said platform along said support means, and means forcontrolling said drive means so that said platform may be positionedrelative to said lifting means so that one or more of said sections areengaged by said lifting means when the latter is raised.
 5. A sheetstacking device as claimed in claim 4 in which each of said sections isprovided with at least one pair of wheels.
 6. A sheet stacking device asclaimed in claim 5 in which said drive means is mounted on one of saidsections and is connected to one pair of its associated wheels.
 7. Asheet stacking device as claimed in claim 5 or claim 8 in which saidsupport means includes a pair of parallel rails spaced to receive thepairs of wheels of the platform sections so as to permit movement ofsaid platform along said rails by said drive means.
 8. A sheet stackingdevice as claimed in claim 1 including means for swinging a section notengaged with said lifting means towards a horizontal position as saidplatform, during lowering thereof, approaches said support means.
 9. Asheet stacking device as claimed in claim 8 in which said swinging meanscomprises a bar pivotally connected at one end to said lifting means,and flexible means connected between the other end of said bar and afixed point positioned above said support means such that as saidlifting means lowers said platform the flexible means becomes taut andcauses said bar to swing about its pivot and contact the section orsections not engaged by said lifting means and swing them into ahorizontal position as said platform approaches said support means.